Pyroelectric detector arrays have the potential to satisfy a number of infrared sensing and imaging applications because of their attractive features of room temperature operation and low cost. They are most suited to operation at moderate frequencies, in the 10 to 100 Hz region, where they can have an NETD of less than 0.2°C, limited by internal detector noise sources. An experimental imager built to evaluate linear pyroelectric arrays is described, and its performance compared with theoretical predictions.

Laboratory evaluation is provided of the improved focal plane array performance realized with a novel optical technique that increases the fill factor of Schottky IRCCD mosaics. Specifically, a lenticulated silicon faceplate is installed on the IRCCD chip to redirect focused image irradiance away from nonsensitive areas in the focal plane and to the infrared-sensitive elements. A technique has been developed for successfully fabricating these optical faceplates with the necessary geometrical requirements. The performance data contained herein were obtained with an RCA-supplied 32 x 63 Schottky IRCCD mosaic having a lenticulated faceplate installed on a portion of the array surface. The adjacent dual construction allowed sensitivity and resolution differences to be easily evaluated under identical operating conditions. The enhanced performance was determined experimentally and then compared to predicted fill-factor improvement.

Defense against detection by thermal infrared imaging systems generally involves the release of various agents along the optical path which act to reduce target contrast in the image. Some obscurants are sufficiently effective to completely obscure the target at visible and infrared wavelengths for reasonably extended periods. The effectiveness of electrooptical systems at threshold contrast levels can be of crucial importance in a wide range of combat scenarios. In modern combat situations critical fire control decisions, either manual or automatic, must often be made in a matter of only a few seconds. Any enhancement of the capability of the electrooptical system can thus be leveraged to very great advantage. There are, of course, numerous digital image processing techniques which can provide the desired target enhancement, however, in most instances these are impractical because of untenable hardware or, more important, time requirements. The ideal solution would involve use of a real time, low cost, simple to use, effective enhancement system. We have evaluated a realtime, analog 3D isometric video system which has been used to enhance low contrast infrared images of a thermally controlled scale tank. A psycho-physical experiment was constructed in which several observers responded to a controlled set of conventional and enhanced infrared images of the target. The experiment clearly demonstrated that the real time enhancement provided by the isometric video system resulted in a significant improvement in low contrast target detectability. Furthermore, the experiment was repeated with simultaneous display of the conventional and enhanced images with the result of still further improvement in low contrast target detectability. We describe the enhancement system and present the results of the evaluation of this device.

High performance thermal imagers, such as the common modules are now readily available. These systems generally employ a scanning mechanism to generate the two dimensional display which makes their adaption to cheap, lightweight, small imagers difficult. However, with the advent of two dimensional close packed arrays of infra-red detectors the development of such a system is now becoming feasible. RSRE and MCCS, Frimley have jointly produced a small imager using cadium mercury telluride detectors. The system has been designed to be adaptable to use both 3-5 μm and 8-14 μm arrays, and to study various electronic correction mechanisms.

In June 1984 the NASA Goddard Space Flight Center issued an RFP for a series of geostationary weather satellites with greatly improved performance. This paper describes key features of the Geostationary Operational Environmental Satellite (GOES)-I,J,K instruments developed by Kodak and submitted to NASA in a proposal effort directed by the RCA Astro-Electronics Division. In order to meet these specifications, alternatives for many instrument features were evaluated prior to selection of a final design. The government's requirements for technical performance and delivery schedule led to an extrodinary development program,

A radiometric budget was developed to determine D-Star requirements for the IR detectors in an improved weather satellite. The analysis developed a model for the signal processing electronics that helped calculate the effective noise bandwidth and which substantially attenuated 1/f noise. The focal plane was designed by evaluating the requirements for power dissipation, number of detectors, image scan rate, processor bandwidth, and detector noise. Calibration will use both a standard blackbody source placed in a thermal-vacuum test chamber and a full aperture panel for in-flight measurements.

The enhancement techniques of infrared image, its theory and main methods are discussed. The paper presents the methods for realizing enhancement of the real time infrared imaging system both in digital and analogous applications. Emphasis is laid on the enhancement techniques of infrared image contour. The concrete project for realizing analog contour enhancement of the infrared image is put forward, and the experimental results are shown.

This paper presents an approach to the design, analysis, fabrication, and a test of a development model of 100 K passive space radiator for a geostationary meteorological satellite. Significant design considerations include the importance of heat-leak control at low temperatures and the importance of a well devised plan for elimination and control of moisture and contaminants. Fabrication issues include the ability of the design to be compatible with spacecraft assembly as well as to accommodate disassembly for repair or access to the focal plane. The results of a test of the development model are presented. The data correlation process is discussed and the need for a good means of determination of surface properties at cold temperatures is identified. A summary of recommended design and fabrication features is presented.

Two causes of nonlinearity are identified in cryogenic radiometric and interferometer systems: (1) multiple time constant response in doped germanium and silicon detectors, and (2) voltage sensitive thick-film resistors used as detector load or transirnpedance feedback resistors. Experimental methods used to evaluated the nonlinear coefficients include the variable source temperature method and the precision aperture method. The effects of nonlinear response upon radiometric systems is minimal: The multiple time con-stant effect results in an "S" shaped response curve as the detector responsivity varies with average signal. The voltage sensitive resistor effect causes a full-scale (10 V) nonlinearity of from 20 to 80%. The effect of nonlinear response upon the performance of an interferometer system results in the generation of false spectral. The linearity data are analyzed using least squares solution so the sensor precision can be determined over the range of measured values. The variable temperature method yields an rms error of about ±10% while the precision aperture method yields an rms error of about ±4% over 4 to 5 orders provided multiple data sets are used to extend the dynamic range of the apertures and to eliminate area dependent data.

A long wave infrared radiance model has been defined that permits modeling of the radiance reaching an aerial or satellite sensor. Given the kinetic temperature and emissivity characteristics of the target and background and the prevailing atmospheric data (e.g. radiosonde) atmospheric transmission (the LOWTRAN transmission code is used to compute integrated transmission as a function of altjtude), upwelled and downwelled path radiance and radiance and contrast at the sensor can be computed. Both Lambertian and specular reflectors can be modeled. The resultant radiance levels were applied to synthetic scenes comprised of silhouettes of ships viewed at various angles and slant paths. By defining certain sensor response functions, the recorded image at the sensor can be modeled. Results are included for viewing in the 8-14 μm region from a fixed altitude AGL through angles from vertical to near horizontal for a single atmosphere.

One of the critical questions regarding radiation thermometers is how to obtain the true temperature of an emitting greybody with an unknown emissivity and with unknown circumferential radiations. In this paper it is suggested that two enclosed chambers with given temperatures and emissivities be used to cover part of the area of the greybody. By using two simultaneous radiothermometer readings, both the true temperature and the emissivity of the greybody can be calculated.

Reliable and meaningful infrared spectroradiometric measurements require careful calibrations and detailed knowledge of specific techniques; often, account has to be taken for atmospheric transmittance, ambient temperature and background changes, and other effects which make measurements complicated. In addition, because of the great advance in quality and quantity of today's infrared based devices, the need has arisen for a large number of measurements in the research and development, production testing and maintenance applications. CI has used a computerized system's approach for these infrared measurement situations, by developing an IBM PC based spectroradiometer with the following capabilities: i) storage of calibration curves in the memory ii) control and display of radiometer parameters iii) signal acquisition and processing iv) calibration and display of calibrated spectra in Watt/cm².sr. and other units v) automatic control of position and temperature of samples to be measured, and position of external optical components vi) modularity of subsystems and software packages

An advanced dynamic infrared (IR) image projection system based on liquid crystal light valve (LCLV) technology is described. The IR-LCLV is capable of presenting a complex IR dynamic image with high spatial and temperature resolution and wide dynamic range at video frame rates. Experimental results obtained from an IR-LCLV utilizing a cathode ray tube as the input source and an extended IR source (blackbody) as the projection beam are presented.

Changes in surface and bulk properties of UDT-05D photodiodes as a result of 1.3 Mrad γ-irradiation are compared. As suspected by previous investiagors but not verified until now, changes in surface properties are seen experimentally to alter significantly overall device characteristics. Changes in device properties include increasesin surface conductivity, improved quantum efficiency at visible wavelengths, decreased dark current at very low reverse bias, decreased infrared response, decreased minority carrier lifetime, and decreased n. The first three results are new and permit differentiation between surface and bulk effects. A model consistent with all these measurements to explain the changes is presented. The model is based upon γ-ray photodesorption of surface impurities.

This paper describes a preliminary investigation of l/f noise in three infrared detector materials used in the MWIR (3-5um). Noise measurements of HgCdTe, PtSi, and InSb detectors were conducted and the results are presented. The various noise sources are discussed.

Semiconductor breakdown in a HgCdTe MIS detector was investigated. The measured breakdown usualy has a surface potential vs. gate-voltage characteristic peak. Calculations based on an ideal MIS model and tunnel theory have failed to explain the observed breakdown characteristics. This paper proposes a breakdown model which considers the influence of dislocations. The dislocations are modeled as excess donor-like impurities captured around each dislocation core. The model explains the peak and predicts the peak height, including its dependence on carrier concentration and dislocation density.

A non-equilibrium mode of operation for semiconductor infrared photodetectors is proposed which will enable their cooling requirements to be substantially reduced. The operating temperature of 3-5 μm band detectors may be raised from - 200K to near ambient, whilst for the 8-12 μm band devices thermoelectric coolers can be considered in place of liquified nitrogen systems. The phenomena of minority carrier exclusion and extraction are utilised in order to maintain the densities of both carrier types well below the near intrinsic, equilibrium values associated with these elevated temperatures, with consequent improvements in responsivity and D.

Nonlinearity in the frequency modulation of the transmitted pulse of a homodyne linear-FM radar will degrade performance. Analysis and computer simulation were performed which provide quantitative results of the effects of nonlinearity on resolution and signal levels obtained from returns from point targets. The anlaysis is based on the expansion of the phase modulation of an individual transmit pulse in a power series in time. Input quantities to the model include magnitudes of non-linearity coefficients, radar parameters, range to target. Experimental data obtained with a laser radar was analyzed and the measured deviation of the frequency modulation from linearity used to predict performance at arbitrary target ranges. Statistical studies of the experimental data yielded information on the consistency of the nonlinearity. Range images obtained with the system are presented which show better than 1 m single-look range resolution.

The high quality In₂0₃/Sn (ITO), In₂0₃ /In, In₂0₃/Cd have been deposited on quatz glass substrates, thermal pressed ZnS and Mgpi, substretes.Then we made transmission measurement in a rather wide range of spectrum which extends from ultraviolet through visible to middle infrared (200A--25μm), and made Hall coefficient measurement, film thickness measurement, energy spectrum analysis, X-ray diffraction, Electrolytic electroreflectance spectra measu-rement, etc. The result of which are discussed based on preliminary analysis and comparison. The square resistance of the film is in the proximity of few tx to fey ten XL. Its optical transmission in the visiblei range as high as 90% and risistivity of 101--2X104.11.-cm, free carriers concentration of 101-1041 col, free cariers mobility of 10-90cm/V.Sec are typically observed.

A comparison of the double exponential model and the equivalent absorption coefficient model as applied to the atmospheric gas nitrous oxide N₂0 is made for low (20 cm ^-1) and high (5 cm ^-1) spectral resolutions. Both models are shown to represent low resolution N₂0 transmittance well. The double exponential model is shown to represent high resolution transmittance better than the equivalent absorption coefficient model does. Comparisons of the double exponential model at low and high resolutions using the same transmittance data base are made. It is shown that virtually no more error occurs when the double exponential model is used to model high resolution N₂0 transmittance as occurs when the double exponential model is used to represent low resolution transmittance.

The optical and electronic design of the Halogen Occultation Experiment (HALOE) elevation sunsensor is described. This system uses a Galilean telescope to form a Solar image on a linear silicon photodiode array. The array is a self-scanned, monolithic charge coupled device. The addresses of both Solar edges imaged on the array are used by the control/pointing system to scan the HALOE science instantaneous-field-of-view (IFOV) across the vertical Solar diameter during instrument calibration, and then maintain the science IFOV four arcmin below the top edge during the science data occultation event. Vertical resolution of 16 arcsec and a radiometric dynamic range of 100 are achieved at the 0.7 micrometer operating wavelength. The design provides for loss of individual photodiode elements without loss of angular tracking capability. The HALOE instrument is a gas correlation radiometer that is now being developed by NASA Langley Research Center for the Upper Atmospheric Research Satellite.

Hemispherically integrated reflectance of snow has been studied both experimentally and theoretically. Spectral measurements in the range of 600 to 2000 nm have been done for several types of snow including meta-morphic states from nearly-fallen to melt-refreezed and density variations from 0.10 to 0.45 g/cm³. The effect of the melting degree up to 20 volume per cent of free water has also been studied. Snow reflection is a multiple scattering phenomenon and it is strongly dependent on the grain size and spectral variations in the ice absorption coefficient. Due to differences between the absorption coefficient of ice and water, the reflection spectrum of dry snow differs from that of wet snow. A reflectance model based on an approximate solution of the radiative transfer equation is used for theoretical analysis. Based on the theory and experiments, it is shown that by using three optimally selected wavelengths the relative free water content and average grain size can be determined. In the experiments of snow with an average grain size of 1 mm, a 0,8 per cent change in the reflectance ratio at wavelengths 1260 and 1370 nm corresponds to one volume per cent variation of the free water content. Reflectance measurement at a third wavelength 1160 nm can be used for computer elimination of grain size de-pendent scattering effects. Further, the reflectance ratio of 1160 and 1260 nm can be used as a measure of the average grain size. For dry snow a change of 1.5 to 2.1 in the reflectance ratio corresponds to an increase of the grain size from 0.25 to 1.5 mm, respectively. The third wavelength 1370 nm can be used here to elimin-ate variations in the free water content. It can be estimated based on the measurements made so far that an accuracy of ±1.5 volume per cent and ±0.2 mm in the measurement of the free water content and average grain size, respectively, can be achieved.

The finite element method was used to analyze the optical performance of the Space Infrared Telescope Facility (SIRTF) fused-silica secondary mirror as it is subjected to a dynamic chopping motion. The chopping motion was assumed to be of quasi-square wave form with the mirror stationary during a dwell period following the actual chop rotation. The primary optical deformation was "ringing" during the dwell period; damping during the dwell time (20 ms) was not effective. For a given chopping motion, the magnitude of the optical deflections could be reduced by proper choice of the support points, by increasing the stiffness of the mirror, reducing the magnitude of the chop angle, and/or increasing the chop period. Prescribed acceleration versus time during the chop motion affects the optical deformations as well. There are optimum support-point locations for each type of motion. Tapering the back of the secondary mirror does not significantly affect optical deformation provided that supports are located at the optimum points. For the best trade of mass moment of inertia against deformation, lightweight mirror geometries should be used.

The fabrication of IR optical fibers for the 2- to l4-μm region is described. Both cylindrical and square fibers fabricated from extruded rods and tubes are discussed. The physical proper-ties of the GeSbSe glasses and optical fibers are reviewed. Fab-rication of different fiber bundles is also reported. The applications of IR optical fibers and bundles are described, and system performance and parametric analysis are developed for some applications, including thermal imaging, IR sensors, CO₂ laser power guide, and low-loss optical fibers.

This paper describes a repetitive spectrally selective shutter that can be installed between the optics and the focal plane to eliminate the requirement for covering the entire optical aperture with a large revolving filter. The optomechanical method used provides rapid "snap-shot" imagery by varying the tilt angle of one or two narrow-bandpass filters, v) that open aperture occurs only when their spectral transmission bands coincide. An optical design configuration allows the spectral shuttering to be performed in the same location normally designated for a chopper wheel. Under these conditions, spectral filter size needs only to encompass focal plane dimensions, rather than match optical aperture diameter as previously required. Ray trace diagrams and graphic plots of transmission versus time and angle are presented which analytically predict the effectiveness of this technique. These results are further substantiated by experimental data obtained in the laboratory. In addition, geometrical, dimensional, and material requirements for optimum two-filter performance are analyzed in detail, together with allowable tolerances.

A radiothermometer for surface temperature measurement is designed with an enclosed cham-ber to eliminate any uncontrolled circumferential irradiation. This paper addresses the signal-to-noise ratio (SNR) and the noise-equivalent temperature difference (NETD) equations in terms of system parameters.